On 18/07/23 04:15, Wenchao Chen wrote:
> When the card is reset, mmc_card_init() will check if this
> card is the previous card by comparing the CID.
>
> If the firmware is upgraded, the product version may change,
> so we remove the product version from the CID check.
What is the use-case for this? I would have thought it is safer
not to assume anything about the card after the firmware has been
upgraded.
>
> Signed-off-by: Wenchao Chen <wenchao.chen@xxxxxxxxxx>
> ---
> drivers/mmc/core/mmc.c | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 89cd48fcec79..32a73378d5c3 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -32,6 +32,9 @@
> #define MIN_CACHE_EN_TIMEOUT_MS 1600
> #define CACHE_FLUSH_TIMEOUT_MS 30000 /* 30s */
>
> +#define MMC_CID_PRV_MASK GENMASK(23, 16)
> +#define MMC_CID_CRC_MASK GENMASK(7, 0)
> +
> static const unsigned int tran_exp[] = {
> 10000, 100000, 1000000, 10000000,
> 0, 0, 0, 0
> @@ -126,6 +129,19 @@ static int mmc_decode_cid(struct mmc_card *card)
> return 0;
> }
>
> +static int mmc_check_cid(u32 *cid, u32 *raw_cid)
> +{
> + /*
> + * When comparing CID, we need to remove the product
> + * version (Field PRV, offset 55:48) and CRC. Because
> + * the product version will change when the firmware
> + * is upgraded. Also, the new CRC is different.
> + */
> + return cid[0] != raw_cid[0] || cid[1] != raw_cid[1] ||
> + (cid[2] & ~MMC_CID_PRV_MASK) != (raw_cid[2] & ~MMC_CID_PRV_MASK) ||
> + (cid[3] & ~MMC_CID_CRC_MASK) != (raw_cid[3] & ~MMC_CID_CRC_MASK);
> +}
> +
> static void mmc_set_erase_size(struct mmc_card *card)
> {
> if (card->ext_csd.erase_group_def & 1)
> @@ -1640,7 +1656,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
> goto err;
>
> if (oldcard) {
> - if (memcmp(cid, oldcard->raw_cid, sizeof(cid)) != 0) {
> + if (mmc_check_cid(cid, oldcard->raw_cid)) {
> pr_debug("%s: Perhaps the card was replaced\n",
> mmc_hostname(host));
> err = -ENOENT;
